David Sweat, left, and Richard Matt. New York State Police A prison break at a maximum-security facility in New York is baffling authorities who are now frantically searching for two murderers on the loose several days after an elaborate escape.

Investigators are trying to figure out "what the rest of the plan was," Rick Mathews, the director of the University at Albany's National Center for Security and Preparedness, told the Associated Press.

"Where were they going to go, and how were they going to do it?"

Richard Matt, 48, was serving a sentence of 25 years to life for killing and dismembering his former boss in 1997. One cop called Matt "the most vicious, evil person I've ever come across in 38 years as a police officer." David Sweat, 34, was serving a life sentence for killing a sheriff's deputy.

They both escaped from the Clinton Correctional Facility in Dannemora, New York, about 20 miles from the Canadian border, over the weekend.

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The escape was elaborate. The pair used power tools to cut through a steel wall in their adjoining cells and escape through a steam pipe, according to Reuters. New York officials suspect the inmates might have had inside help in obtaining the power tools and breaking out, and the police are now questioning a woman who worked at the prison and might have been an accomplice.

"I can assure you these individuals could not have done this by themselves," Kevin Tamez, a managing partner for the New York-based MPM Group, told Business Insider. MPM provides security consulting for many federal and state prisons.

New York State Governor's Office

"A search revealed that there was a hole cut out of the back of the cell through which these inmates escaped," acting state corrections commissioner Anthony Annuci said Saturday at a news conference.

"They went onto a catwalk which is about six stories high," Annuci added. "We estimate they climbed down and had power tools and were able to get out to this facility through tunnels, cutting away at several spots."

For the prisoners to "get into the bowels of the prison — the catwalk and all that — they'd need help," Tamez said.

"My question is — I understand it's an old prison, and it was in need of some upgrades — yet you have an area that sensitive down there [the catwalk], and it's not alarmed, there's no motion detectors, there's nothing to alert the staff?" he said. "That's mind-boggling to me."

The prisoners most likely planned their escape for weeks, Martin Horn, former commissioner of the New York City Department of Correction, told Business Insider.

New York State Governor's Office

The two convicts may have been able to identify weak links in the prison's operations or taken advantage of loose tools.

"As these prisons get older, they require a lot of attention ... and as a result the prisons have to rely on outside contractors," Horn said. "Outside contractors may or may not comply with [the protocols]. A worker might be reluctant to report the tool as being lost over fear of losing their job."

Because of the information and planning required to pull off an escape this seamlessly, Tamez echoed speculation about the involvement of someone with "intimate knowledge of the design of that prison," as he put it.

"The lighting wasn't great down there, I can guess, but they knew exactly where to go and what pipes to cut," Tamez added. "I'd like to think it wasn't a prison employee or a former prison employee" who may have helped the escape.

The area where two convicted murderers used power tools to cut through steel pipes, also leaving a note, at a maximum-security prison in Dannemora, New York, near the Canadian border. Darren McGee/New York State Governor's Office, via AP

The prisoners might also have been able to figure out the layout of the prison's back channels through work on a maintenance crew.

"Behind each of these cells there are pipes and wires … that allow service access," Horn said. "It's not uncommon to use prisoners as part of the maintenance work, so it's entirely possible that these guys had been on a maintenance crew … and had observed the layout."

Blueprints downloaded from a smartphone with internet access could have also aided the duo.

"The smuggling of cellphones and smartphones into prisons has become a plague all over the country," Horn said.

As for the sawing required to cut through the steel wall and pipes, the inmates might have worked at that slowly over an extended period of time.

"These are big cell blocks … and there are periods of the day where it can be very noisy," Horn said. "They're timing those officers and they know what their routines are, so they know when the noise will be masked and the officers aren't there to observe them."

The manhole from which the prisoners escaped. New York State Governor's Office